1. Field of the Invention
The present invention is related to a method and apparatus for feeding a pulverized material for a glass melting furnace and, in particular to a method and apparatus for feeding a pulverized material for a glass melting furnace which can continuously operate with a back pressure during the unloading of the pulverized material.
2. Related Prior Art
Melting glass has been done in different kinds of furnaces and of the types of fuels, depending on the final characteristics of the product and also regarding the thermal efficiency of the melting and refining processes. Unit melter furnaces have been used to melt glass (by means of gas fuel), these furnaces have several burners along the sides of the furnace, the whole unit looks like a close box where there is a chimney that can be placed either in the beginning of the feeder or at the very end of the furnace, it means, in the downstream of the process. However there is an enormous heat loss in the glass leaving high-temperature operating furnaces. At 2500xc2x0 F., for example, the heat in the flue gases is 62 percent of the heat input for a natural gas fired furnace.
In order to take advantage of the remaining heat of the flue gases, a more sophisticated and expensive design come out, named as the regenerative furnace. It is well known that, to operate a regenerative glass melting furnace, a plurality of gas burners are associated with a pair of sealed regenerators disposed side-by-side. Each regenerator has a lower chamber, a refractory structure above the lower chamber and an upper chamber above the structure. Each regenerator has a respective port connecting the respective upper chamber with a melting and refining chamber of the furnace. The burners are arranged to burn fuel, such as natural gas, liquid petroleum, fuel oil or other gaseous or liquid fuels which are suitable for use in the glass melting furnace and thereby supply heat for melting and refining the glass making materials in the chamber. The melting and refining chamber is fed with glass making materials at one end thereof at which is located a doghouse and has a molten distributor disposed at the other end thereof, which comprises a series of ports through which molten glass may be removed from the melting and refining chamber.
The burners may be mounted in a number of possible configurations, for example a through-port configuration, a side-port configuration or an under-port configuration. Fuel, e.g. natural gas, is fed from the burner into the incoming stream of pre-heated air coming from each regenerator during the firing cycle, and the resultant flame and products of combustion produced in that flame extend across the surface of the melting glass, and transfer heat to that glass in the melting and refining chamber.
In operation, the regenerators are cycled alternately between combustion air and exhaust heat cycles. Every 20 minutes, or 30 minutes, depending on the specific furnaces, the path of the flame is reversed. The objective of each regenerator is to store the exhausted heat, which allows a greater efficiency and a higher flame temperature that could otherwise be the case with cold air.
For operating the glass melting furnace, the fuel fed to the burners and the combustion air supplied is controlled by measuring at the port mouth and the top of the structure, the quantity of oxygen and combustible material present so as to ensure that within the melting chamber or at points along the melting chamber, the combustion air fed is controlled in excess to that is required for combustion of the fuel being supplied, to ensure a complete combustion of the fuel.
However, due to the continuing upward spiral of energy costs (primarily natural gas), this have forced that the major float glass, containers and tableware manufacturers to add xe2x80x9csurchargesxe2x80x9d to truckloads of flat glass, bottles and other glass articles. Natural gas prices have increased over 120% this year (in Mxc3xa9xico), far above previous estimates.
Taking into account the above, the present invention is related to the use a pulverized material as a source of fuel for melting glass and more specifically to a method and apparatus for metering a pulverized material to a furnace for melting glass.
Apparatuses for the continuous gravimetric metering of pourable material are know in the art. Gravimetric metering systems are generally adopted in application when the exact measurement and control of the material in question are of fundamental importance (pharmaceutical industry, chemical industry, cement industry, glass industry, food industry, etc.) or where the flows involved are so small that the error which occurs if a volumetric metering system is used is not tolerable.
Examples of the gravimetric metering apparatuses for pourable material are illustrated in the U.S. Pat. Nos. 4,528,848, 4,661,024, 5,184,892, 5,353,647, 5,670,751 and 6,041,664.
For example the U.S. Pat. No. 4,528,848 of Hans Hxc3xa4fner is related to a device for continuous, gravimetric metering and pneumatic conveying of pourable material provides that a material stream is conveyed over a measuring path while charging a load measuring device and the product of moment load and conveying speed is formed. The conveyor is in the form of a rotor having an essentially vertical axis and conveyor pockets in the form of chambers or cells which are moved with the rotor in a circular orbit over the measuring path. A housing surrounds the rotor in a pressure tight manner and includes a charging aperture and an emptying aperture which are rotationally displaced from one another. A load measuring device is connected to the housing and a tachometer is provided for measuring the angular velocity of the rotor. A pneumatic conveying system is provided which has feed lines respectively communicating with an air feed aperture in the housing and the emptying aperture.
The U.S. Pat. No. 4,661,024 of Hans W. Hxc3xa4fner is related to a method for operating an apparatus for continuous gravimetric metering and feeding of pourable material conveyed by a conveyer through a metering path, the conveyer including a rotor provided with conveyer pockets, having an essentially vertical axis and being arranged within a housing in a tightly sealed manner, the housing being provided with a charging station and a discharging station the latter including ports for connecting a pneumatic feeding system, wherein a gas is supplied to spaces within the housing and the rotor outside the metering path.
The U.S. Pat. No. 5,184,892 of Hans W. Hxc3xa4fner is related to a system and a method for continuous gravimetric metering, pneumatic conveying and/or mixing of pourable materials using metering apparatuses of a type such as e.g. disclosed in U.S. Pat. No. 4,528,848.
The U.S. Pat. No. 5,353,647 of Ludger Toerner is related to an apparatus for measuring a bulk material mass flow by measuring Coriolis forces that are caused by the mass flow passing through a winged wheel. The mass flow is introduced centrally onto the winged wheel, which rotates with a constant r.p.m. and diverts the mass flow radially outwardly. The Coriolis forces and thus the corresponding reaction torques which are proportional to the mass through-flow are measured with the aid of a torque joint interposed between a housing of the winged wheel and a drive motor for the shaft that drives the wheel. Force sensor elements, preferably in the form of bending beams, are incorporated into the torque joint and are deflected by the reaction torque moment applied to the motor housing. These bending beams provide an output signal that is proportional to the mass through-flow through the apparatus.
Other apparatus related to a gravimetric metering of bulk material is claimed in the U.S. Pat. No. 5,670,751 of Hans Wilhelm Hxc3xa4fner which includes a weighting container which is supported on at least one weighing cell connected to a weighing electronics and is connected by flexible connections to a bulk material feed line and a discharge line, wherein a pressure sensor is provided on the weighing container for detecting the pressure in the weighing container and the pressure sensor is connected to the weighing electronics for registering a weighing signal only when a limit pressure value is attained.
And finally, the U.S. Pat. No. 6,041,664 also of Hans W. Hxc3xa4fner es related to a method and an apparatus for continuous, gravimetric metering and mass flow determination of flowable material, with a flowmeter, especially a Coriolis measuring wheel, for determining the instantaneous mass flow and a metering device downstream of the flowmeter.
However, one of the main problems of the apparatuses for metering a pourable material is that, during the moment that the pulverized material is being unloading, a back pressure in the discharge of the material is provoked. This effect makes that the pulverized material be feeding in an irregular form provoking problems in the discharge and conveying of the pulverized material.
Other problem of the apparatuses of the previous art is that the many of the apparatuses were development for handling large quantities of pulverized material (up of one ton), which are extremely expensive and complex.
As can be seen of the above there are various types of apparatuses for the metering of a pourable material, each one designed in accordance to different objectives and applications in the industry.
In view of the foregoing, the present invention is related to a method and an apparatus for feeding a pulverized material for a glass melting furnace and some other applications, which supply a constant flow of the pulverized material to a series of burners that are associated with said glass melting furnace, in a relation side by side. Said pulverized material is feeding in a continuous form to burn the pulverized fuel in a melting and refining zone of the glass furnace. The pulverized material is mixed with air for feeding an air-fuel mixture toward each one of the cited burners for the melting of glass.
According with the above the present invention is related to an apparatus for feeding a pulverized material comprises: a first storage container including an upper section and a lower section, said first storage container having charging and discharging ports, respectively, to receive and to discharge a constant flow of a pulverized material; a separation chamber attached below of the first storage container, said separation chamber including an upper inlet and lower outlet, said upper inlet and said lower outlet being alternately opened and closed, to fill up or to empty out the separation chamber with the pulverized material, wherein the material entering is settled out under the influence of gravity forces into said separation chamber; a second storage container including an upper section and a lower section, the upper section of said second storage container being connected with the lower outlet of said separation chamber, for alternately filling the second storage container in accordance to a predetermined storage level or weight; discharging means attached to the lower section of second container for continuously discharge the pulverized material; pneumatic conveying means arranged with said discharging means for conveying the material discharged from the discharging means; and weighing means associated with the second storage container for controlling the filled up and emptied out of said second storage means in accordance with said predetermined storage level.
It is an object of the present invention to provide a method and apparatus for feeding a pulverized material for a glass melting furnace which can continuously operate with a back pressure during the unloading of the pulverized material.
It is a further objective of the present invention to provide a method and apparatus for feeding a pulverized material for a glass melting furnace, which is of a simple design, which is handling quantities of pulverized material from between 100 Kg/hr to 1600 kg/hr.
It is another objective of the present invention to provide a method and apparatus for feeding a pulverized material for a glass melting furnace, that is capable of dosing the pulverized material in an continuous form, with a minimal negative air pressure.
These and other objectives and disadvantages of the present invention will be evident to the experts in the field from the following detailed description of the invention, which is illustrated in the attached drawings.